Final answer:
The best definition of 'abysmal' in the given context is 'terrible, indicating a low level of performance' since it contrasts the student's expectation with the high achieving outcome of earning an A. The correct option is (b).
Step-by-step explanation:
Based on the use of context clues in the sentence, the best definition of abysmal is b. terrible, indicating a low level of performance. The student expected their performance to be abysmal, but since they actually earned an A, we can infer that abysmal means something along the lines of very poor or of a low standard. This is contrary to the positive outcome, which was an A grade, thereby highlighting the significant difference between the expected and actual performance. The use of abysmal here is to describe an expectation of a very low quality outcome, which is consistent with the broader meaning of the word.